Method of making sulfuric acid.



PATENTED JULY 3, 1906.

W. McA. JOHNSON.

METHOD OF MAKING SULFURIO ACID.

APPLICATION FILED OCT. 10, 1903.

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Specification of Letters Patent.

latented July 3, 1906.

Application filed October 10. 1903. Serial No. 176,611-

To all whom it may concern:

Be it known that I, WOOLSEY MoA. JOHN- SON, a citizen of the United States, residing at Iola, in the county of Allen and State of Kansas, have invented certain new and useful Improvements in Methods of Making Sulfuric Acid, of which the following is a specification.

This-invention is a method of making sulfuric acid by electrolytic oxidation of sulfur dioxid or sulfurous acid. It has heretofore been proposed to electrolytically oxidize sulfur dioxid, the gas being injected into the electrolyte through a carbon anode or in proximity to the anode. In such cases the reaction proceeds with separation of sulfur at the cathode, and it has been proposed to keep such separated sulfur from the anode by means of a diaphragm interposed between the electrodes.

According to the preferred embodiment of my invention the sulfur dioxid is oxidized in an electrolytic cell or tank provided with anodes of lead, the electrodes being connected according to the series system-that is to say, in such manner that the intermediate or unconnected plates act as bipolar electrodes. Under these conditions the sulfur dioxid dissolved or otherwise retained in the bath is oxidized at the anodes to sulfuric acid. For the cathode surfaces it is desirable to use a metal having. a low. cathode potential, whereb the cathodic separation of sulfur is reduce to a minimum. For this purpose copper electrodeposited upon the cathode surfaces is preferred.

My preferred procedure is as follows: Sulfuric-acid solution of about twent per cent. concentration is saturated with su fur dioxid by means of a coke-tower or other suitable device. This solution is then caused to flow through the electrolytic cell and past the electrodes therein, whereb the sulfur dioxid is oxidized to sulfuric aci and a solution is obtained which may approach thirty per cent.

. concentration. A certain proportion of said acid is withdrawn and concentrated or utilized in any desired manner, while the remaining portion, diluted withwater to twenty per cent. and again saturated with sulfur dioxid, is returned to the electrolytic cell, this cycle of operations being repeated indefinitely.

If desired, sulfur dioxid may also be inj ected into the electrolytic cell, and the temand so arran ed therein that t perature of the solution may be lowered to any desired extent to increase the quantity of sulfur dioxid held in solution therein.

For a clear understanding-of my invention reference is made to the accompanying drawings, wherein- F i ure 1 is a central longitudinal section of one orm of electrolytic cell suitable for the production of sulfuric acid according to my method. Fig. 2 is a plan view of the same, and Fig. 3 is a modification illustrating the use of electrodes whose anode and cathode faces are composed of dissimilar metals.

Referring to Figs. 1 and 2, 1 indicates a tank or containing vessel which may be constructed of cement, lead-lined wood, enameled iron, or other material substantially unafiected by the electrolyte. 2 3 4 represent electrodes disposed transversely of said tank e electrolyte is caused to ow alternately over and under the plates. It will be understood that the electrodes may "be otherwise arranged in the tank. For instance, lateral passages may be provided between the electrodes and the side of the tank or through the electrodes themselves in such manner as to direct the elec trolyte in a tortuous path, or any other suitable arrangement for causing the electrolyte to flow past the active surfaces of the electrodes may be used. The intermediate electrodes 3 have no metallicconnection with the circuit and accordin ly act as bipolar electrodes,- that face of each electrode late which is nearest the anode acting as acat ode, and the opposite face of each plate acting as an anode, as is well understood. The end electrodes 2 4 are the terminals of the electric circuit. Appropriate inlet and discharge passages 7 8 are provided for the solution. a

In the modification illustrated in Fig. 3 the anode connection is-assumed to be made at plate 2 and said late is preferably formed of a sheet of lead Plate 4, to which the cathode connection is made, may consist of a sheet of copper or of lead faced with copper. The intermediate plates 3, of which an desired number are used, are in this em odiment of my invention formed of sheets of lead 5, having electrodeposited upon their cathode surfaces a layer of metallic copper 6, which, b reason of its low cathode potential in the so ution, serves to reduce the uantity of sulfur separated by cathodic re uction. While I consider this to be the preferred form I to, but may employ anode surfaces of platinum.

In operation, the lead anode surfaces become eroxidized and the sulfur dioxid containe in the electrolyte becomes oxidized to sulfuric acid, said oxidation being probably effected, in part, at least, through the agency of the lead eroxid on the anodes. The injection of su fur dioxid into the bath, in addition to increasing the concentration of the product, serves to prevent the formation of persulfuric acid. Any traces of sulfur which may be formed are conveniently removed from the solution by boiling to coagulate the sulfur and subsequently filtering.

By the ex ression a solution containing sulfur dioxi as herein em loyed, I intend to include solutions in whic the sulfur dioxid may exist in combination, as solutions of sulfurous acid.

I claim 1. The herein-described method of producing sulfuric acid, which consists in electrolyzing a solution containing sulfur dioxid by means of electrodes electrically connected in series, the anode faces being com osed of lead and the cathode faces of a meta having a low cathode potential, substantially as described.

2. The herein-described method of producing sulfuric acid, which consists in electro;

lyzing a solution containing sulfur dioxid by means of electrodes electrically connected in series, the anode faces being composed of lead and the cathodef'aces of copper, substantially as described.

3. The herein-described method of producing sulfuric acid, which consists in electrolyzing a solution containing sulfur dioxid by means of electrodes electrically connected in series, the anode faces being composed of lead and the cathode faces of elee'trcsdepesited copper, substantially as described.

4. The herein described continuous method of making sulfuric acid, which consists in electrolyzin a solution of sulfuric acid containing sul ur dioxid, thereby increasing the concentration of the sulfuric acid in solution, withdrawing a portion of the solution, diluting the remaining portion, introducing thereinto further quantities of sul fur dioxid, and repeating the electrolysis, substantially as described.

5. The herein described continuous method of making sulfuric acid, which consists in electrolyzing a solution of sulfuric acid containing sulfur dioxid by means of electrodes electrically connected in series, thereby increasin the concentration of the sulfuric acid in so ution, withdrawing a portion of the solution, diluting the remaining portion, introducing thereinto further quan tities of sulfur dioxid, and repeating the electrolysis, substantially as described. I

6. The herein, described continuous method of making sulfuric acid, which con.- sists in electrolyzin a solution of sulfuric acid containing sull ur dioxid by means of electrodes electrically connected in series, the anode faces being composed of lead and the cathode faces of cop er, thereby increasin the concentration 0 the sulfuric acid in so ution, withdrawing a portion of the solution, dilutin the remaining portion, introducin therelnto further quantities of sulfur dioxi and repeatin the electrolysis, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

WOOLSEY MoA. JOHNSON. Witnesses:

CHARLES M. STARKWEATHER, JOHN FELT MoRRIs. 

